Bright Light Can Help Seasonal Affective Disorder

Medically Reviewed

Some people with seasonal affective disorder (SAD), which is the temporary depression that develops during the shorter, darker days of winter, can be successfully treated with exposure to bright light for up to an hour each day.

People with SAD feel hopeless for no evident reason, lose interest in people or things they normally enjoy, are fatigued and unproductive, have difficulty concentrating, sleep too much, and find it hard to get out of bed.

In one study, 57 percent of 191 people with SAD responded to light therapy. In another study, light therapy was comparable in effectiveness to antidepressant therapy but worked faster and caused fewer side effects.

And in a major review of 173 published studies, bright-light therapy yielded substantial relief for both SAD and mild to moderate depression that was not linked to seasonal changes.

Bright lights: What to expect

The therapy involves sitting in front of a bank of full-spectrum lights. A bright-light box contains fluorescent tubes, a reflector, and a diffusing screen. Many of these boxes emit 10,000 lux, which is a measurement of light intensity. (By comparison, typical indoor evening room light is usually less than 100 lux, and a bright office might be less than 500 lux.)

Improvement can often be seen within a few days, with symptoms disappearing after two to three weeks. Continued light therapy is needed to prevent a relapse.

A doctor typically would have a patient sit in front of a 10,000-lux box for 30 minutes right after waking up each morning. Bright light therapy is generally considered to be safe. Side effects, which are usually infrequent, mild, and short-lasting, may include eyestrain, blurred vision, agitation, irritability, headache, and nausea.

Although commercially available light boxes are advertised for depressed people, these devices are not approved by the U.S. Food and Drug Administration. Light therapy should be used only with your doctor’s guidance, as it can cause side effects when used improperly. For instance, light therapy may trigger manic symptoms in people who have bipolar disorder.